9 Most Common Internal Horse Parasites
and pasturepoor environments. Horses inadvertently ingest a mite that carries the infective stage of the parasite. The parasite then matures into a worm and attaches to areas of the digestive system specifically the end of the small intestines called the ileum and the start of the large intestines called the cecum4 . These attachment sites are clinically significant because a large tapeworm burden in this area can lead to gastrointestinal motility problems and lifethreatening forms of colic. Once attached the tapeworm sheds eggfilled segments to be excreted in manure.
Ascarids
Ascarids are a major cause of colic in foals and weanlings5 but natural immunity is developed as a horse ages past about a year old. Ascarid eggs are remarkably hardy and remain viable in the environment. Once ingested by the foal they hatch and release larvae. These larvae migrate through
A dewormer that causes the worms to die at once can lead to obstruction as well so a careful deworming program specific to foals should be developed.
Pinworms